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The dispersive interaction between a qubit and a cavity is ubiquitous in circuit and cavity quantum electrodynamics. It describes the frequency shift of one quantum mode in response to excitations in the other and, in closed systems, is necessarily bidirectional, i.e., reciprocal. Here, we present an experimental study of a nonreciprocal dispersive-type interaction between a transmon qubit and a superconducting cavity, arising from a common coupling to dissipative intermediary modes with broken time reversal symmetry. We characterize the qubit-cavity dynamics, including asymmetric frequency pulls and photon shot noise dephasing, under varying degrees of nonreciprocity by tuning the magnetic field bias of a ferrite component in situ. We introduce a general master equation model for nonreciprocal interactions in the dispersive regime, providing a compact description of the observed qubit-cavity dynamics agnostic to the intermediary system. Our result provides an example of quantum nonreciprocal phenomena beyond the typical paradigms of non-Hermitian Hamiltonians and cascaded systems.
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This content will become publicly available on November 13, 2025
Asymmetric Transmittance and Nonreciprocity in Guided Wave Circuits: Fundamentals and IC topology
In a reciprocal system, all the wave travels in the same way backward as forward. When the exchange between the source and detectors result in different transmittance, non-Hermiticity is granted but the nonreciprocity needs to be carefully evaluated. Although most of the integrated circuits are reciprocal, unexpected nonreciprocal response may emerge in the system, especially the tunable components containing asymmetrically coupled resonators, traveling wave electrodes and hysteresis response. The nonreciprocity may result in unexpected signal distribution, distortion and errors in analogue circuits of electrical and photonic networks. With proper engineering, the nonreciprocity can be leveraged and optimized for suppressing the laser noise in photonic systems as isolators, reducing the circuits duplication as circulators. The radio-frequency nonreciprocity can be used for protecting the high power amplifiers from oscillation and damage. Asymmetric coupling can also be useful in simplifying the circuit complexity and reducing crosstalk in the optical interconnect transceiver circuits.
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- Award ID(s):
- 2338546
- PAR ID:
- 10557707
- Publisher / Repository:
- IEEE
- Date Published:
- Journal Name:
- IEEE solidstate circuits magazine
- Volume:
- 16
- Issue:
- 4
- ISSN:
- 1943-0582
- Page Range / eLocation ID:
- 54-61
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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